a Beaker cache before accessing the database:

    * A "region", which is a cache region argument passed to a 

      Beaker CacheManager, specifies a particular cache configuration

      (including backend implementation, expiration times, etc.)

    * A "namespace", which is a qualifying name that identifies a

      group of keys within the cache.  A query that filters on a name 

      might use the name "by_name", a query that filters on a date range 

      to a joined table might use the name "related_date_range".

    When the above state is present, a Beaker cache is retrieved.

    The "namespace" name is first concatenated with 

    a string composed of the individual entities and columns the Query 

    requests, i.e. such as ``Query(User.id, User.name)``.

    The Beaker cache is then loaded from the cache manager based

    on the region and composed namespace.  The key within the cache

    itself is then constructed against the bind parameters specified

    by this query, which are usually literals defined in the 

    WHERE clause.

    The FromCache and RelationshipCache mapper options below represent

    the "public" method of configuring this state upon the CachingQuery.

    """

    def __init__(self, manager, *args, **kw):

        self.cache_manager = manager

        Query.__init__(self, *args, **kw)

    def __iter__(self):

        """override __iter__ to pull results from Beaker

           if particular attributes have been configured.

           Note that this approach does *not* detach the loaded objects from

           the current session. If the cache backend is an in-process cache

           (like "memory") and lives beyond the scope of the current session's

           transaction, those objects may be expired. The method here can be

           modified to first expunge() each loaded item from the current

           session before returning the list of items, so that the items

           in the cache are not the same ones in the current Session.

        """

        if hasattr(self, '_cache_parameters'):

            return self.get_value(createfunc=lambda: list(Query.__iter__(self)))

        else:

            return Query.__iter__(self)